Patent GB-600206-A (GB)
Title: Improvements in and relating to the preparation of acids and esters
IPC: C07C51/10
Filed: 1945-04-27
Abstract: In a process for the production of esters of aliphatic dicarboxylic acids by condensing the alcohol esters of formal-substituted aliphatic mono-carboxylic acids with carbon monoxide in the presence of an acid catalyst (see Group IV (b)), the acid catalysts specified are hydrochloric, sulphuric, phosphoric or tungstic acids, inorganic acidic salts, e.g. potassium acid sulphate, sodium acid phosphate and boron fluoride and the acidic catalysts designated in U.S.A. Specifications 1,924,766, 2,037,654 and 2,053,233, which include inorganic acids, e.g. those of P, As, B, with or without volatile halides and certain specified metal halides supported on charcoal or other supports; hydrogen halides in presence of active carbon; and phosphoric acid or calcium iodide supported on activated charcoal.ALSO:Esters of aliphatic dicarboxylic acids are produced by condensing the alcohol esters of formal-substituted aliphatic mono-carboxylic acids having the formula ROCH2OR1COOH in which R is an alkyl group or an aliphatic residue and R1 is a divalent straight or branch chain aliphatic hydrocarbon group, with carbon monoxide in the presence of an acid catalyst, e.g. hydrochloric, sulphuric, phosphoric or tungstic acids, inorganic acidic salts, e.g. potassium acid sulphate, sodium acid phosphate and boron fluoride and the acidic catalysts designated in U.S.A.  Specifications 1,924,766, 2,037,654 and 2,053,233 which include inorganic acids, e.g. those of P, As, B, with or without volatile halides and certain specified metal volatile halides and certain specified metal halides supported on charcoal or other supports; hydrogen halides in presence of active carbon; and phosphoric acid or calcium iodide supported on activated charcoal. The reaction is preferably conducted at 20 DEG  C. to 350 DEG  C. and under 5 to 1500 atmospheres pressure.  The esters may be hydrolysed to the corresponding acids.  Suitable esters used are those of alkoxy methoxy-carboxylic acids, such as methoxy-, ethoxy-, iso- and normal propoxy- or butoxy-and the higher alkoxy methoxy acids derived from acetic, propionic and higher straight and branch chain aliphatic acids.  Particularly suitable are the p  methyl, ethyl, normal and isopropyl and normal and isobutyl esters.  The acids and their esters may be prepared by the process described in U.S.A.  Specification 2,250,487, comprising reacting a methylene glycol diether with glycollic acid or an ester of glycollic acid or a partially dehydrated glycollic acid in the presence of a dehydrating catalyst.  When alkoxy methoxy acetic acid ester is used as starting material, the product contains the esters of diglycollic acid, of methoxyacetic acid, of hydroxyacetic acid and higher boiling liquid residues.  The esters may be fractionated and the high boiling fraction treated with an alcohol such as methanol or ethanol containing sulphuric acid or this treatment with an alcohol may be carried out before fractionation and repeated if necessary after fractionation.  In examples: (1) methoxymethoxy-acetic acid methyl ester is reacted with carbon monoxide in a silver-lined shaker tube with boron trifluoride as catalyst.  The product is boiled with methanol containing sulphuric acid and subsequent distillation under reduced pressure yields methyl methoxyacetate, methyl glycollate, dimethyl glycollate and a higher boiling liquid residue.  The latter is then boiled with methanol containing sulphuric acid and the product yields methyl methoxy acetate, methyl glycollate, dimethyl diglycollate and higher boiling products; (2) ethyl ethoxymethoxy acetate, isopropyl isopropoxymethoxy-acetate and isobutyl isobutoxy-methoxy acetate are each condensed with carbon monoxide as in (1), the products being diethyl-, di-isopropyl-, di-isobutyl - diglycollates respectively; (3) CH2(OCH2OCH2COOCH3)COOCH3 is condensed with carbon monoxide as in (1) to yield an unsymmetrical diester of diglycollic acid, which when alcoholized gives dimethyl diglycollate and methyl glycollate; (4) dimethyl diglycollate obtained as in (1) is hydrolysed with water which may contain a hydrolysis catalyst such as sulphuric acid or phosphoric acid.  The methanol formed is distilled off and the acid obtained by crystallization.  The process may also be effected continuously and in this and the batch process the by-products may be returned to the reaction zone.  In a continuous process mentioned for the production of a diester of diglycollic acid, carbon monoxide and an alcohol ester of an alkoxy methoxy acetic acid are passed together with an acid catalyst into a heated reaction zone under pressure and the diester continuously withdrawn.